Radial compressor

ABSTRACT

A radial compressor, in particular radial compressor of an exhaust gas turbocharger, with an impeller, a stationary housings, a main flow passage defined by the housing for feeding a medium to be compressed in the direction of the impeller, and a secondary flow chamber arranged radially outside the main flow passage, which is delimited from the main flow passage by a contour wall and which is connected to the main flow passage via a secondary flow opening in the region of the impeller. Seen in the meridian section, the secondary flow opening, via which the secondary flow chamber is connected to the main flow passage in the region of the impeller, is set obliquely or inclined relative to a radial direction.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to a radial compressor.

2. Description of the Related Art

From EP 2 194 277 A1 a radial compressor of an exhaust gas turbocharger is known. Accordingly, EP 2 194 277 A1 shows a radial compressor with a rotating impeller and a stationary housing. The housing defines a main flow passage in order to conduct compressed medium in the direction of the impeller. Outside the main flow passage, a secondary flow chamber is arranged, which is delimited from the main flow passage by a contour wall. According to EP 2 194 277 A1, the secondary flow chamber extends, starting from a suction region of the main flow passage, as far as to a secondary flow opening in the region of the impeller. In the region of the impeller, the secondary flow chamber is connected to the main flow passage via the secondary flow opening. Struts, which connect the contour wall, which delimits the main flow passage from the secondary flow chamber, run within the secondary flow chamber. According to EP 2 194 277 A1, the secondary flow opening, via which the secondary flow chamber is connected to the main flow passage in the region of the impeller, extends, seen in the meridian section, in the radial direction.

By way of such a secondary flow chamber, which is connected to the main flow passage, the characteristic map stability and thus the operating behaviour of a radial compressor can be improved to a certain extent.

With increasing throttling of the radial compressor, the working medium to be compressed in the compressor undergoes a sufficient pressure build-up even in the inlet region of the impeller, so that the working medium, via the secondary flow chamber, recirculates in the main flow passage opposite to the flow direction, wherein in this way in a recirculation mode the aerodynamic stability with reduced rates of delivery of the compressor can be achieved.

If there are major demands on the throughput of the radial compressor, a pressure drop is created in the inlet region of the impeller, which has the consequence that the working medium flows via the secondary flow chamber in a direction that replaces itself in the flow direction through the main flow passage, so that the secondary flow chamber is then not flowed through in the recirculation mode but in a bypass mode. By way of this, high rates of delivery of the radial compressor can then be realised.

SUMMARY OF THE INVENTION

There is a need for further improving the characteristic map stability of a radial compressor. There is a need, in particular, to increase the stable working range in the direction of further reduced rates of delivery and the intake capacity of the radial compressor.

Based on this, an object of one aspect of the invention is to create a new type of radial compressor. According to the invention, the secondary flow opening, seen in the meridian section, via which the secondary flow chamber is connected to the main flow passage in the region of the impeller, is set obliquely or inclined relative to a radial direction. With these measures, the stability of the working range of the radial compressor can be further improved. In particular, the working range can be increased with regard to further reduced rates of delivery and with respect to the intake capacity.

According to an advantageous further development, the secondary flow opening, seen in the meridian section, via which the secondary flow chamber is connected to the main flow passage in the region of the impeller, includes an angle between 10° and 80°, preferably an angle between 10° and 70°, particularly preferably an angle between 20° and 70°, most preferably an angle between 20° and 60° with the radial direction. With these angle ranges, in which the secondary flow opening, seen in the meridian section, is inclined relative to the radial direction, the stable working range of the radial compressor can be particularly preferably expanded, in particular for providing further reduced rates of delivery and for expanding the intake capacity.

Preferred further developments of the invention are obtained from the subclaims and the following description. Exemplary embodiments of the invention are explained in more detail by way of the drawing without being restricted to this.

Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

The figure is a schematic meridian section through a radial compressor according to the invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The figure shows a cross section by way of an extract through a preferred exemplary embodiment of a radial compressor 10 according to one aspect of the invention.

A radial compressor 10 comprises a rotating impeller 11 with multiple moving blades 12. Furthermore, a radial compressor 10 comprises a stationary housing 13. The housing 13 of the radial compressor 10 defines a main flow passage 14 for the medium to be compressed, in order to conduct the medium to be compressed via the main flow passage 14 in the direction of the impeller 11. Outside the main flow passage 14, the housing 13 defines a secondary flow chamber 15. A contour wall 16, which is also described as annular web, delimits the main flow passage 14 from the secondary flow chamber 15.

The secondary flow chamber 15 extends from a section upstream of the impeller 11 as far as into the region of the impeller 11. Accordingly, the Figure shows that upstream of the impeller 11 a first secondary flow opening 17 is formed, via which the secondary flow chamber 15 seen in the flow direction of the medium to be compressed, is connected to the main flow passage 14 upstream of the impeller 11. A second secondary flow opening 18 is formed in the region of the impeller 11, via which the secondary flow chamber 15 is connected to the main flow passage 14 in the region of the impeller 11.

Struts 19 extend within the secondary flow chamber 15. By way of the struts 19, the contour wall 16 is connected to the housing 13.

That secondary flow opening 18, via which the secondary flow chamber 15 is connected to the main flow passage 14 in the region of the impeller 11, is set obliquely relative to a radial direction R seen in the meridian section according to one aspect of the invention.

Seen in the meridian section, the secondary flow opening 18, via which the secondary flow chamber 15 is connected to the main flow passage 14 in the region of the impeller 11, includes an angle a with the radial direction R. This angle a is between 10° and 80°, preferably between 10° and 70°, particularly preferably between 20° and 70°, most preferably between 20° and 60°.

In a particularly preferred embodiment of the invention, the angle a amounts to 25°±15°, preferentially 25°±10°, preferentially 25°±5°.

Through the embodiment according to one aspect of the invention, the secondary flow opening 18, via which the secondary flow chamber 15 is connected to the main flow passage 14 in the region of the impeller, the following advantages can be achieved.

On approaching the surge limit of the radial compressor, a recirculation of the medium to be compressed in the radial compressor is favoured in the region of the secondary flow chamber 15. In the Figure an arrow I depicts the recirculation of the working medium through the secondary flow chamber 15, namely starting from the secondary flow opening 18 in the region of the impeller 11 in the direction of the secondary flow opening 17 upstream of the impeller 11 opposite to the flow direction of the main flow, which is visualised by the arrow III in the Figure.

On approaching the capacity limit or choke limit of the radial compressor, a bypass flow through the secondary flow chamber 15 is favoured, wherein such a bypass flow is depicted by the arrow II in the Figure. This bypass flow II serves for providing high rates of delivery in the region of the choke limit or capacity limit and is directed starting from the secondary flow opening 17 upstream of the impeller 11 in the direction of the secondary flow opening 18 in the region of the impeller 11. This bypass flow II can be fed to the main flow almost without throttling effects. Accordingly, not only the surge limit but also the capacity limit or choke limit can be expanded.

Because of this, the working range of the radial compressor can ultimately be substantially expanded. In a turbocharger, which utilises the radial compressor according to one aspect of the invention, the efficiency can be increased. Furthermore, a faster response behaviour during load switching can be realised.

Transition contours of the secondary flow opening 18 in the region of the impeller 11 to the housing 13 and to the contour wall 16 can be embodied with sharp edges or rounded.

The secondary flow opening 18 is preferentially embodied as a slot circulating in the circumferential direction.

Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto. 

What is claimed is:
 1. A radial compressor, comprising: a rotating impeller; a stationary housing; a main flow passage defined by the stationary housing configured to feed a medium to be compressed in a direction of the impeller; a secondary flow chamber arranged radially outside the main flow passage, which is delimited from the main flow passage by a contour wall and which is connected to the main flow passage via a secondary flow opening in the region of the impeller; a meridian section the secondary flow opening, via which the secondary flow chamber is connected to the main flow passage in the region of the impeller, is set obliquely or inclined relative to a radial direction.
 2. The radial compressor according to claim 1, wherein in the meridian section the secondary flow opening, via which the secondary flow chamber is connected to the main flow passage in a region of the impeller, includes an angle between 10° and 80° with the radial direction.
 3. The radial compressor according to claim 2, wherein in the meridian section the secondary flow opening includes an angle between 10° and 70° with the radial direction.
 4. The radial compressor according to claim 3, wherein n the meridian section the secondary flow opening includes an angle between 20° and 70° with the radial direction.
 5. The radial compressor according to claim 4, wherein in the meridian section the secondary flow opening includes an angle between 20° and 60° with the radial direction.
 6. The radial compressor according to claim 1, wherein the secondary flow chamber is connected to the main flow passage in a flow direction of the medium to be compressed upstream of the impeller via a further secondary flow opening.
 7. The radial compressor according to claim 1, wherein the radial compressor is a radial compressor of an exhaust gas turbocharger. 